There are two main classes of 3D auto-stereoscopic displays based on different approaches: “space multiplexing (sharing)” and “time sequencing (sharing)”.
The main disadvantage of 3D auto-stereoscopic displays using space-sharing approach is that the resolution of the 3D image is reduced with increasing the number of perspective views forming the 3D image in the field of view. This results in 3D image quality degradation and restriction of its viewing angle.
Unlike space-sharing displays, 3D auto-stereoscopic time-sequencing display systems reproduce 3D image with resolution that doesn't depend on the number of perspective views. This allows widening 3D image viewing angle by increasing the number of perspective views without reducing resolution of the 3D image.
There are several projection 3D display systems known in the prior art that embody the time-sequencing approach and use at least two lens matrices (arrays), for example, the ones described in U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2 and US Patent Application US 2005/0270645.
US Patent Application US 2005/0270645 describes a 3D display apparatus comprising a display component for generating a sequence of 2-dimensional (2D) images and an image scanning assembly consisting of a first lens matrix (array), a second lens matrix (array) optically coupled to the first lens matrix (array) via intermediary optical assembly.
The peculiarity of this scanning assembly consists in that the first lens array can be made significantly smaller than the second array, if the intermediary optical assembly is a magnification system. This allows shifting the first lens array for scanning images instead of shifting the second array that can be made much larger and thereby significantly reduce the mechanical complexity of the scanning operation and provide more compact 3D display systems. This is much more suitable for 3D display systems with large screens.
However, this advantage is achieved at the expense of increased cross-talk. There are two sources of cross-talk in the image scanning assembly described in US Patent Application US 2005/0270645. One of them (the first source) is associated with shifting the structure of optical beams at the second lens array (shown FIG. 1, Prior Art) relative to the structure of the second lens array during the scanning operation. The second source of cross-talk is associated with a mismatch between the structure of 2D images at the first lens array shifting during the scanning operation and the structure of this array.
It is worth noting that the level of cross-talk for both sources grows with the amplitude of the displacement of the first lens array, resulting in 3D image quality degradation and restriction of its viewing angle.
It should be noted that the second source of cross-talk could be eliminated if the first lens array is displaced together with the display component. But, the associated mechanical complexity may effectively cancel the advantage of using a small-size first lens array. Therefore, it is necessary to find another solution for this cross-talk problem.
The said crosstalk problems can be partially solved by using the solution describing 3D display systems disclosed in the prior art (U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2). Each of these systems comprises a display component for generating a sequence of 2-dimensional (2D) images, an image scanning assembly consisting of a first lens matrix (array) and a complex of two (second and third) lens matrices (arrays), and a mechanism for transversely moving the first matrix or the complex of matrices relative to each other to provide the scanning operation.
In fact, the use of three lens arrays significantly reduces the level of cross-talk related to the said first source of cross-talk, thus allowing better quality of the 3D image and wider viewing angles. This is provided by the fact that during the scanning operation an optical beam passing through each lens of the second lens array is directed by the said lens to the respective lens of the third lens array within the aperture of the latter lens.
Meanwhile, the said second source of cross-talk is inherent in both 3D display systems disclosed in the respective versions of U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2 associated with the movement of the first matrix and in those of US 2005/0270645. This prevents further improvement of the quality of the 3D image and widening of its viewing angle.
Besides, the possibility of using the solution disclosed in U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2 for implementation of large-screen 3D display systems is restricted because of higher mechanical complexity of the scanning apparatus.
It should be noted that implementation of large-screen 3D display systems based on both the solution disclosed in U.S. Pat. No. 7,944,465 B2 and U.S. Pat. No. 8,243,127 B2 and the solution disclosed in US 2005/0270645 is unfeasible without reducing the level of cross-talk mentioned above.
Therefore, it is necessary to find another solution for implementation of large-screen 3D display to solve prior art problems related to cross-talk and to the mechanical complexity of the scanning operation.